Memory storage density is a measure of the quantity of information (i.e., bits) that can be stored on a given length of track, area of surface, or in a given volume of a computer storage medium. Generally, higher density is more desirable, because it allows greater volumes of data to be stored in the same physical space. Density therefore has a direct relationship to storage capacity of a given medium. Density also generally has a fairly direct effect on the performance within a particular medium, as well as price. Hard drives store data in the magnetic polarization of small patches of the surface coating on a (normally) metal disk. The maximum areal density is constrained by the size of the magnetic particles in the surface, as well as the size of the “head” used to read and write the data.
To increase areal density, magnetic recording systems have begun using “shingled” writing schemes, in which newly written tracks partially overwrite previously written tracks. This has the effect of narrowing the previously written tracks, with resulting widths less than the width of the write head. As a result, track density and therefore areal density is increased. However, read-back signals associated with “shingled” writing schemes exhibit increased inter-track interference (ITI), with resulting adverse effects on bit-error and sector-error rates (BERs and SERs). For example, in a shingled writing scheme, a newly written track is labeled n while adjacent, partially overwritten tracks are labeled n−1 and n+1. Magnetic recording typically employs a ‘write wide, read narrow’ strategy. In such a scenario, the minimum lithographic feature for magnetic recording is the magnetic read width (MRW), and, as such, is a critical dimension in future areal density improvements. In present shingled writing systems, MRW is typically 60% of track pitch (TP). Scaling track pitch, for instance, to achieve areal density gains would require a smaller MRW. However, smaller MRWs result in decreased signal-to-noise ratio (SNR) and increased occurrence of head instabilities. A system that overcomes the limitations of MRW to increase areal densities would therefore be desirable.